Methods of the kind described are known in many forms, just as substances for the practice of the known methods have been proposed in many forms, namely, as so-called boiler scale prevention agents of both inorganic and organic nature. The mechanism of all known methods or measures is based on binding the inorganic salts dissolved in the water which touches the heated surfaces by complex formation, thus to increase their solubility. It has been found, however, that the known measures do not work satisfactorily in practice. Usually, the use of the known boiler scale prevention agents fails, for the reason that they are not efficient enough in the temperature range above 100.degree. C.
The problem underlying the invention is to develop a method of the kind described herein which works satisfactorily also at temperatures of over 100.degree. C. Another object of the invention is to provide compositions and combination substances which are especially suited for the practice of the new method.